Motor drive position movement profile calibration

ABSTRACT

A slowdown profile calibration method and apparatus for a position regulated motor drive system is disclosed, including a programmed digital computer as the position controlling component of such a system that is calibrated to optimize the operation of said motor drive system in regard to distance error points and corresponding to a defined operational speed pattern relative to those distance error points.

United States Patent Robertson Oct. 24, 1972 [541 MOTOR DRIVE POSITION3,574,280 4/1971 Smith, Jr. ..72/8

MOVEMENT PROFILE CALIBRATION Primary Examiner-Eugene G. Botz [72]Inventor. James D. Robertson, Pittsburgh, Pa. Atmmey p H. Henson at al'[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa. [57] ABSTRACT [22] Filed: June 14, 1971 A slowdownprofile calibration method and apparatus for a position regulated motordrive system is dis- [211 Appl' l52787 closed, including a programmeddigital computer as the position controlling component of such a system[52] US. Cl. ..444/1, 318/561, 72/6 that is calibrated to optimize theoperation of said [51] Int. Cl. ..B21b 37/12, G06f 9/00, H02 3/00 motordrive system in regard to distance error points [58] Field of Search ..31 8/7; 235/15 1.1; 444/ 1 and corresponding to a defined operationalspeed pat tern relative to those distance error points. [56] ReferencesCited 25 Claims, 30 Drawing Figures UNlTED STATES PATENTS 2,066,8721/1937 Adams et a1. ..3 l 8/? X IB l 3e MEMORY INPUT CONTROL OUTPUT 7SCREWDOWN CONTROL i i 42 I L ARITHMETIC SOFT WARE PROGRAMS SCREWDOWNPOSITION SHEET 01 0F 13 I 20 I I sCREwDOwN sCREwDOwN SCREwDOwN CONTROLCONTROL CONTROL I l I I u-u-n-n-n I I I I I SCREwDOwN i sCREwDOwN IsCREwDowN POSITION P I POSITION POSITION DE ECTOR I DETECTOR I DETECTORI CONTROL COMPUTER I INPUT OPERATOR OUTPUT DEVICES smi DEVICES MEMORY xI 1 I ,'20' I PUT CONTROL OUTPUT sCREwDowN CONTROL ".42 I I ARITHMETICI2 I6 I4 sCREwDOwN POSITION ,36 DETECTOR SOFTWARE PROGRAMS "FICIP'ATEN'TEDnm24 1972 SHEET OBUF 13 NEE 5 P'ATENTEMD 24 m2 3. 700.379SHEET 10 OF 13 SPEED DRIVE REGULATOR MOTOR ENCODER LOADER PROGRAM 7FUNCTIONS PR Y COMMON OGRAM m ACQUIR SUBROUTINES 1 (Has) FORTRAN (2)READIMFIGB) 528532: (a) PRTMSG(FIG.9)

OPERATOR'S PROGRAMMER ("DSTOPT PRTPRHFIGJO) CONSOLE CONSOLE 3 I (Hes)PROGRAM (5) TRAVEUFIGJ n (s) PRODAT(FIG.|2)

7)PRINTP (FIG-n FWDDO(FIG.I3)

' (B) REVDO(FIG.I4)

(smcnvr (FIGS) POSTOMFIGJS) FIG. I?

SPEED DRIVE REGULATOR MOTOR ENQODER 306 POSITION CONTROLLER DESIREDPOSITION PATENTEI] 02124 I972 VERIFICATION OF 80 POSITION FIG.2IA

SPEED -so +'s0 osmou FI 6.22 A

TO CALIBRA'TE s| v2 (2ND TRY) -s'o +sb SI 3 POSITION F I 623A ToCALIBRATESI VI 0 LL! E v0 I l SIO I POSITION FIG.2IB

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I I so s| s2 POSITION o CALIBRATE 52 v2 (2ND TRY) FIG.25A

v2 a g w w r'""'"" FIG.25B a (n I 7 v0 I I so s1 s2 POSITION MOTOR DRIVEPOSITION MOVEMENT PROFILE CALIBRATION BACKGROUND OF THE INVENTION forJanuary 1965 at pages 71 to 76, and as generally described in apublished article entitled Small Control Computers-A New Concept by F.G. Willard which appeared in the Westinghouse Engineer for November 1964at pages 174 to 179. Two other published articles of interest here inregard to providing a background understanding of theprogramming of aprocess control computer should be noted; one article was published inthe January 1965 Westinghouse Engineer at pages 13 to 19 by Paul E.Lego, and the other article was published in the 1966 Iron and SteelEngineer Yearbook at pages 328 to 334, by J. S. Deliyannides and A. H.Green.

Each such computer control system is typically associated withpredetermined input systems, which can include an input system thatscans process signals representing the status of various processoperating conditions, a conventional analog input system which scans andconverts process analog signals and operator controlled and other inputdevices and systems which could include paper tape, teletypewriter anddial input apparatus. Various kinds of information are entered into thecomputer control system through information input devices, includingdetected process operational signals, hardware oriented programs andcontrol programs for the programming system and so forth. The inputsystem interfaces the computer control system with the controlledprocess through the medium of measured or detected signals. To effectdesired output control actions, control devices are operated directly bymeans of an output or by means of analog signals derived from the outputsystem through a digital to analog converter. One such control actioncould output from the computer control system the desired speed controlsignal for controlling the operation of the speed regulator operativewith the drive motor in the screwdown motor drive for each stand of arolling mill operative in accordance with the teachings of the presentinvention. A suitable output display can be provided for operation withthe computer control system in order to keep a human operator generallyinformed about the controlled process operation and in order to signalthat operator regarding an event or condition relative to any particularhappening which may require some action on his part.

When a given rolling mill stand is first assembled and made ready tobegin the thickness reduction of workpieces passed between the rolls ofthat stand, it is desired to calibrate the slowdown profile curve, suchas illustrated by the data stored in TABLE THREE, to compensate foroperational factors of the position regulated screwdown motor drivesystem such as inertia, friction, response of speed regulator andresponse times of any associated programmed digital control computer. Itmay later become desirable to again calibrate the provided slowdownprofile curve in relation to subsequent wear of mechanism parts, such asbearings, screws and so forth, as well as changed lubrication andfriction conditions.

SUMMARY OF THE INVENTION The position regulated motor drive systemslowdown profile calibration operation in accordance with the presentinvention can be operative as the normal dayto-day recalibration or as atechnique for optimizing the correlation of selected distance errorpoints to correspond with defined speed points for controlling theoperation of a given position regulated motor drive system, such as thescrewdown motor drive of a rolling mill stand, when no workpiece ispresent between the rolls. The optimization is accomplished relative toa predetermined data file for the particular motor drive system to becalibrated by modifying the forward and reverse slowdown profile curvesof that data file so that the desired accuracy band is stored in thelast error point and the desired travel movements are stored throughoutthe remainder of the profile in predetermined locations respectively.

When a given distance error point, corresponding to a defined speedpoint, is being calibrated, the motor drive system is positioned so thata theoretical position error exists which is equivalent to the presenterror point minus one. Thusly, for a given distance error point S to becalibrated, the present error point S is made equivalent for the purposeof this calibration to the previous calibrated error point (S-l Themotor drive is then positioned relative to the present distance errorpoint, and each time an overshoot occurs the present error point iscorrected by a first factor corresponding to a predetermined portionsuch as threefourths of the resulting position overshoot or undershootplus a second factor of one encoder bit increment for stability. Afterno overshoot or undershoot occurs, a predetermined number, such as five,of consecutive positioning attempts are completed to make certain thatno position overshoot or undershoot occurs, and thereafter the minimumor optimum distance calibration is considered to be found relative tothis particular defined speed point. This calibration operation iscontinued until all the desired position error points for each slowdowncurve are calibrated in both the up movement direction and the downmovement direction for the motor drive system to be calibrated.

BRIEF DESCRIPTION OF THE DRAWINGS, TABLES AND PROGRAM LISTINGS FIG. 1 isa schematic showing of a tandem rolling mill including a screwdowncontrol, operative to determining the operation of a screwdown motor foradjusting the roll spacing of each mill stand, and a screwdown positiondetector for each said mill stand operative with a control computer fordetermining the operation of the position regulated screwdown motordrive system for each such stand;

FIG. 2 is a schematic illustration of the position re gulated motordrive system operative with a typical rolling mill stand, with thecontrol computer being illustrated for functioning as a positioncontroller in accordance with an optimum distance calibration programapplied to the control computer;

FIG. 3 shows an illustrative functional flow chart of calibrateddistance optimization program DSTOPT in accordance with the teachings ofthe present invention and PROGRAM LISTING TEN;

FIG. 4 shows an illustrative functional flow chart of the operatorsfunction initiation routine program LOADER in accordance with PROGRAMLISTING ONE;

FIG. 5 shows an illustrative functional flow chart of the data filetransfer to calibration area routine program ACQUIR in accordance withPROGRAM LIST- ING TWO;

FIG. 6 shows an illustrative functional flow chart of the data filetransfer from calibration area routine program ACTIVT in accordance withPROGRAM LIST- ING THREE;

FIG. 7 shows an illustrative functional flow chart of the slowdown curveprintout routine program PRINTP in accordance with PROGRAM LISTING FOUR;

FIG. 8 shows an illustrative functional flow chart of the read inoperator input routine program READIN called by the distanceoptimization program and in accordance with PROGRAM LISTING FIVE;

FIG. 9 shows an illustrative functional flow chart of the message outputroutine program PRTMSG in accordance with PROGRAM LISTING SIX;

FIG. 10 shows an illustrative functional flow chart of the print curvesroutine program PRTPRF called by the distance optimization calibrationprogram and in accordance with PROGRAM LISTING SEVEN;

FIG. 1 1 shows an illustrative functional flow chart of the allowabletravel determination routine program TRAVEL called by the distanceoptimization program and in accordance with PROGRAM LISTING EIGHT;

FIG. 12 shows an illustrative functional flow chart of the profile datalocation routine program PRODAT called by the distance optimizationprogram and in accordance with PROGRAM LISTING NINE;

FIG. 13 shows an illustrative functional flow chart of the forwardslowdown profile modification routine program FWDDO called by thedistance optimization program and in accordance with PROGRAM LISTINGTWELVE;

FIG. 14 shows an illustrative functional flow chart of the reverseslowdown profile modification routine program REVDO called by thedistance optimization program and in accordance with PROGRAM LISTINGTHIRTEEN;

FIG. 15 shows an illustrative functional flow chart of the positionroutine program POSTON called by each of the F WDDO program and theREVDO program and in accordance with PROGRAM LISTING FOUR- TEEN;

FIG. 16 illustrates the restricted movement range operative with theTRAVEL program;

FIG. 17 is an illustrative showing of the slowdown profile calibrationmethod and apparatus of the present invention with a control computer;

FIG. 18 is a schematic illustration of a well known position regulatedmotor drive system operative for controlling the position of a drivemotor, such as the screwdown motor for a rolling mill stand;

FIG. 19 is a curve illustrating the theoretical slowdown profile of amotor drive system, such as shown in FIG. 18, with the actual slowdownprofile shown as a solid line of such a motor drive system in relationto the desired slowdown profile shown as a dotted line;

FIG. 20 illustrates the theoretical maximum acceleration followed by amaximum deceleration operation of a typical motor drive system;

FIGS. 21A and 21B illustrate the verification of the positioning withinthe defined accuracy band;

FIGS. 22A and 22B illustrate the first iteration calibration operationrelative to a position error point S1;

FIGS. 23A and 23B illustrate the second iteration calibration operationof the motor drive system relative to the position error point S1;

FIG. 24 illustrates the first iteration calibration operation relativeto a position error point 82; and

FIG. 25 illustrates the second iteration calibration operation relativeto the position error point S2.

TABLE ONE at the end of the specification illustrates the initialdistance error points for which it is desired to calibrate a typicalmotor drive system in relation to the operating speed of the motor foreach of said distance error points.

TABLE TWO at the end of the specification illustrates the operatordefined motor speed points corresponding to the initial distance errorpoints shown in TABLE ONE.

TABLE THREE at the end of the specification illustrates the calibrateddistance error points for each of the defined motor speed points andwhich calibration results from the operation of the slowdown profilecalibration method and apparatus of the present invention.

TABLE FOUR at the end of the specification illustrates the arrangementof the data file stored in the memory of the control computer for atypical motor drive system.

PROGRAM LISTING ONE at the end of the specification illustrates asuitable LOADER program in accordance with the flow chart of FIG. 4.

PROGRAM LISTING TWO at the end of the specification illustrates asuitable ACQUIR program in ac cordance with the flow chart of FIG. 5.

PROGRAM LISTING THREE at the end of the specification illustrates asuitable ACTIVT program in accordance with the flow chart of FIG. 6.

PROGRAM LISTING FOUR at the end of the specification illustrates asuitable PRINTP program in accordance with the flow chart of FIG. 7.

PROGRAM LISTING FIVE at the end of the specification illustrates asuitable READIN program in accordance with the flow chart of FIG. 8.

PROGRAM LISTING SIX at the end of the specification illustrates asuitable PRTMSG program in accordance with the flow chart of FIG. 9.

PROGRAM LISTING SEVEN at the end of the specification illustrates asuitable PRTPRF program in accordance with the flow chart of FIG. 10.PROGRAM LISTING EIGHT at the end of the specification illustrates asuitable TRAVEL program in accordance with the flow chart of FIG. 1 1.

PROGRAM LISTING NINE at the end of the specification illustrates asuitable PRODAT program in accordance with the flow chart of FIG. 12.

PROGRAM LISTING TEN at the end of the specification illustrates asuitable DSTOPI program in accordance with the flow chart of FIGS. 3Aand 3B.

PROGRAM LISTING ELEVEN at the end of the specification illustrates asuitable DATA program within the understanding of persons skilled inthis particular art.

PROGRAM LISTING TWELVE at the end of the specification illustrates asuitable FWDDO program in accordance with the flow chartof FIG. 13.

PROGRAM LISTING THIRTEEN at the end of the specification illustrates asuitable REVDO program in accordance with the How chart of FIG. 14.

PROGRAM LISTING FOURTEEN at the end of the specification illustrates asuitable POSTON program in accordance with the flow chart of FIG. 15.

DESCRIPTION OF A PREFERRED EMBODIMENT The present invention relates tothe calibration of position regulated motor drive systems, and moreparticularly to the calibration of the operation of such a motor drivesystem suitable for use with a metal rolling mill stand.

In the operation of a metal reversing or tandem metal rolling millstand, the unloaded roll opening and the speed of that stand are set upby an operator or by a programmed digital computer control system toproduce workpiece reductions resulting in delivered work product at thedesired thickness. Since the set up conditions can be in error and sincecertain mill parameters affect the stand loaded roll opening during theactual workpiece rolling operation and after set up conditions have beenestablished, a stand gauge control system is employed to control thestand delivery gauge or thickness. For the purpose of the desiredoperation of the stand gauge control system, it is important that areliable and accurate position regulated screwdown motor drive system beoperative for the purpose of accurately positioning the work rolls ofeach stand in accordance with the desired reference position of thosework rolls for the purpose of reducing a workpiece during each pass ofthe workpiece between the rolls in accordance with a desired reductionschedule.

In FIG. 1 there is shown a tandem rolling mill including a series ofreduction rolling stands S1, S2 through Sn, with only three of thestands being shown. However, it should be understood that five or six oreven seven stands may be included. A workpiece enters the rolling millat the entry end and is elongated as it is transported through thesuccessive stands S1 through Sn to the delivery end of the mill. Theentry workpiece would have a known steel grade and known thickness andwould have a known width. The delivered workpiece would haveapproximately the same width, with the delivery gauge or thickness beingbased upon the production order for which the workpiece is intended.Each stand produces a predetermined reduction or draft, such that thetotal mill draft reduces the entry workpiece to a desired final deliverythickness. Each stand is conventionally provided with a pair of workrolls between which the workpiece 10 is passed. A large DC drive motoris controllably energized at each stand to drive the corresponding workrolls at a predetermined speed. a

To vary the unloaded work roll opening at each stand, a pair ofscrewdown motors 12, which operate in conjunction with each other toform a screwdown motor drive system as shown in FIG. 1, are provided ateach stand. The respective screwdown mechanisms 14 clamp the oppositeends of the backup rolls and thereby apply pressure to the work rolls ateach stand. Normally the two screwdown mechanisms 14 at a particularstand would be in identical positions, but they can be located atdifferent positions for the purpose of strip guidance during threadingor for other purposes. It should be noted that the provision of anelectric motor 12 driving a screwdown mechanism 14 to control the standroll opening can be replaced by a hydraulic positioning servo system ora hydraulic motor operated with a screwdown mechanism if desired.

A screwdown position detector 16 provides an electrical signalrepresentation of the screwdown controlled roll opening position at eachroll stand.

A programmed digital control computer 18 is provided to automaticallycontrol the operation of the tandem mill, including each positionregulated screwdown motor drive system as may be desired. Preferably thecontrol computer 18 comprises a programmed process control digitalcomputer which is interfaced with the various mill sensors and thevarious mill control devices to provide control over many of the variousfunctions involved in operating the tandem mill shown in FIG. 1.According to the user preference, the control computer 18 can alsoinclude conventional manual and/or automatic analog controls for backupoperation in performing preselected mill functions. The control computer18 can include a central integrated process control or set up processorwith associated input/output equipment, such as is included in thePRODAC 2000 (P2000) control computer system currently sold in the openmarketplace by the Westinghouse Electric Corp.

The computer-processor is associated with predetermined input systemsnot specifically illustrated in FIG. 1, which typically include aconventional contact closure input system to scan'contacts or othersignals representing the status of various process conditions, aconventional analog input system which scans and converts process analogsignals, operator controlled and other information input devices such aspaper tape, teletypewriters and dial input devices. Various kinds ofinput information are entered into the digital computer system throughthe input devices including, for example, desired strip delivery gaugefrom each of the rolling mill stands and workpiece temperature,workpiece strip entry thickness and width by entry detectors if desired,grade of steel being rolled, any selected workpiece plasticity tables,hardware oriented programs and control programs for the programmingsystem associated with the control computer and so forth. The contactclosure input system and the analog input system interface the controlcomputer system with the controlled process through the medium ofmeasured or detected variables. In addition, contact closure outputsystems can be associated with the various control devices operated inresponse to control actions calculated or determined by execution of thecontrol programs in the control computer 18. To effect these determinedcontrol actions, the control devices are operated directly by means ofoutput system contact closures or by means of analog signals derivedfrom output system contact closures through a digital to analogconverter. One such control action includes the screwdown positioningsystem commands, which are applied to the respective screwdown controls20 for each of the rolling mill stands for controlling the operation ofthe associated screwdown motor drives 12 for the desired screwdownmovement of the respective rolling mill stands. Display and print outequipment can be included such as teletypewriter systems associated withthe output of the control computer 18, in order to keep the milloperator generally informed about the mill operation, and in order tosignal the operator regarding an event or alarm condition which mayrequire some action on his part.

In FIG. 2 there is schematically shown a position regulated motor drivesystem for controlling the roll opening of a typical rolling mill stand,which can be the single stand of a reversing slab mill. The screwdowndrive motor 12 is operated with a screwdown control 20 for controllingthe operation of the screwdown mechanism 14 as required to adjust theunloaded roll opening between the rolls 30 and 32 of the rolling millstand operative with a workpiece 10. The encoded signal from thescrewdown position detector 16 in accordance with the unloaded rollopening between the rolls 30 and 32 is supplied through an input section34 of the control computer 18 through which all input signals areapplied, including the information generated by the associated softwarecontrol programs 36. The control computer 18 conventionally alsoincludes a memory section 38, a control section 40, an arithmeticsection 42 and an output section 44, as well known to persons skilled inthe operation of pro grammed digital computers. The output section 44supplies the desired screwdown reference position signal to thescrewdown control 20.

A prior art publication of interest for a more detailed backgroundunderstanding of the hardware and software operation of the PRODAC 2000Control Computer System is the PRODAC 2000 Computer Systems ReferenceManual, which has been published and made available by the WestinghouseElectric Corp.

For a typical reversing single stand slab mill the screwdown movementsare usually in the range of l to 30 inches, however, the most commonmovements, which may include about 80 percent of all movements, are inthe order of 1% to 3 inches. The total screwdown travel for a typicalslab mill may be in the order of inches to 60 inches, and consideringthe movement of the rolls from the time that the workpiece first entersthe work rolls on a first pass, until the workpiece has left the rollsafter the last pass, a total movement in the order of 30 inches may beinvolved. Most of the movements for the succeeding passes followgeneralized patterns between l% and 3 inches for each movement.Accordingly, it is desirable to minimize the time required to make themore common screw movements, such as a three inch movement betweensuccessive passes or a 2 inch movement between successive passes or a 1%inch movement between successive passes. The maximum edge and flat draftpasses are typically 3 inches and 2 inches and a torque limited passwould probably be less than 2 inches and in the order of 1% inches.

The optimum distance calibration in accordance with the teachings of thepresent invention has substantial value in regard to these most commonlymade calibrated distance error point, such as from 1.75 to 1.45, theoperator could lower the corresponding defined speed point of 20 percentto something like 17 percent and then recalibrate the distance errorpoint accordingly. This operation can be repeated as necessary until thecalibrated distance error point of about 1.45 is realized. It is verycommon in the actual operation of a reversing single stand mill for thespeed of movement of the screwdown motor drive system to be a limitingfactor relative to the time required for the operation of the mill inrelation to the making of successive passes. For a tandem strip mill thescrewdown motor drive system speed is perhaps less of a limitation thanit is for a reversing single stand mill.

For predetermined position movements S1, S2 through SN, and utilizing asubstantially constant deceleration after a previous substantiallyconstant acceleration for the purpose of effecting these desired travelor position movements, the screwdown motor drive system should in theoryfor optimum operation first accelerate at a substantially constant andmaximum acceleration until the substantially constant and maximumdeceleration curve is reached, and the screwdown motor drive wouldsubsequently follow the deceleration curve until the work rolls arrivedat the desired reference position. The constant acceleration curve andthe constant deceleration curve are predetermined as substantially themaximum available movement curves for the motor drive system to follow.

in accordance with the present invention, the characteristic positionerror movements or travel distances S1, S2 through SN are selected inadvance and each optimized individually in relation to the minimum timerequirements to effect the desired movement in the position of the workrolls, to change the spacing between the unloaded rolls in accordancewith the defined travel movement or position error. The fastest mannerfor making the desired change in position is to follow the maximumacceleration curve until it intersects with the maximum decelerationcurve without the requirement for any interval of movement at asubstantially constant velocity.

The practice of the present invention typically will allow the saving oftwo-tenths or three-tenths of a second in the positioning of thescrewdown motor drive system for a given position error. Considering thenumber of such changes that are made in the course of a normal 8 hourrolling mill stand work shift, a substantial amount of operating time issaved to thereby permit a substantial increase in the quantity of workproduct passing through the rolling mill stand. The typical screwdownmotor drive system may require in the order of 1 second to go from zeroto full speed in its normal operation. In the operation of a typicalreversing single stand mill, the workpiece is passed through the millstand and then must wait a sufficient time interval for a desiredposition error movement or adjustment to be made in the spacing betweenthe rolls of the stand before the workpiece can be passed through therolls a succeeding time. One purpose of the present invention is todecrease the time duration of this waiting period that the workpiecemust undertake before the rolling mill stand is ready for a succeedingpass of the workpiece between the rolls.

When the distance optimization data file for a given mill stand isdetermined by the control computer in ac cordance with the teachings ofthe present invention, better data is available for controlling theoperation of the mill stand than is available when a manual slowdowncalibration is attempted. A human operator has to make one setting ofthe screwdown position control parameter and then watch the resultantmoveinent of the rolls by means of an oscilloscope or the like; thehuman operator cannot accomplish the optimum distance movement profilecalibration such as can be accomplished with the programmed controlcomputer system in accordance with the teachings of the presentinvention. In addition, the latter distance movement profile calibrationwill extend over three-fourths of the entire adjustment range of therolling mill stand. Also, the programmed control computer utilizes aniterative method which permits a very small increase or change in thescrewdown motor drive system operating speed for succeeding positionadjustments in an effort to reach the optimum profile for the distanceslowdown curve. A human operator may require in the order of one-half ofa day to a full day to calibrate the screwdown motor drive system for asingle rolling mill stand, and the end result of the human operatorcalibration is not as good as the end result of the calibration inaccordance with the present invention. In comparison, the method andapparatus of the present invention will require only about minutes toprovide a more precise position movement calibration of the screwdownmotor drive system.

The present slowdown profile calibration technique requires less timefor the actual calibration and in addition provides a more optimumslowdown control profile for each position movement made by thescrewdown motor drive system during the workpiece rolling operation ofthe mill stand such that a substantially improved operation of theposition regulated motor drive system also results from the practice ofthe present invention. The accumulated time saving provided bytwo-tenths or three-tenths of a second less time being required for themaking of each pass of a workpiece through the calibrated rolling millstand over the usable life of that rolling mill stand provides aconsiderable and valuable saving in time. A typical initial pass with agiven workpiece 6 feet long may take one second to 1% seconds tocomplete the pass. Whereas, the final pass with the same workpiece inthe order of 50 feet long will take considerably longer for completion.It is the reversal time between the tail end of the workpiece leavingthe mill stand on a given pass and the head end of the workpieceentering the same mill stand moving in the opposite direction on asucceeding pass which is reduced by two-tenths or threetenths of asecond, and this reversal time may be typically in the order of 2seconds.

The distance movement optimization control program of the presentinvention functions with a defined or established speed of operation foreach desired position error point. The control program incrementallychanges the position error point for a given defined speed to find anoptimum position error point for operation at that defined speed withoutan overshoot or undershoot occurring in the final position of thescrewdown motor drive system. The distance error point is initially madesmaller for the purpose of intentionally getting an overshoot and thenis incrementally brought back toward the desired position error pointuntil an overshoot or undershoot does not occur, which in effectprovides a vernier change in the definition of the position error pointrelative to a previously established or defined speed point. Theovershoot is corrected in accordance with a predetermined factor, suchas three-fourths, of the resulting overshoot plus one bit increment, todetermine the incremental change that will made in the position errorpoint to remove the overshoot condition of operation and thesubstantially constant and maximum acceleration and deceleration curvesare utilized as was previously described. The selection of the speedpoints by the operator should be such as to provide the speed referencesignal from the position controller to the speed regulator of the motordrive system (as shown in FIG. 18) for maximum optimum speed ofoperation of the screwdown motor drive system for effecting a desiredposition change for each distance error point without an overshoot orundershoot condition occurring.

One practical purpose of the present distance optimization program is tofind for each defined speed point for the operation of the motor drivesystem, the minimum distance error point for suitable operation of themotor drive system to in effect increase the operating speed of thescrewdown motor drive system as much as can be realized without anovershoot or undershoot in the resulting position setting for thescrewdown mechanism and still be within the permissible zero errortolerance band. For each defined speed point it is desired to find theminimum position error point for which the screwdown motor drive systemcan operate at the defined speed point without an overshoot orundershoot occurring in the resulting position setting of the screwdownmechanism. A fundamental limitation on the operation of thescrewdownmotor drive is the predetermined maximum acceleration curve MA and thepredetermined maximum deceleration curve MD for the motor drive system,as generally set forth in FIG. 20.

The teachings of the present invention include the operation of a motordrive system position optimization control program, for the calibrationof a position regulated motor drive system, such as a screwdown motordrive system operative for determining the roll opening between the workrolls of a rolling mill stand. A LOADER program is operative as a partof this control program, as well as a plurality of predeterminedfunction programs and common subroutine programs for accomplishing thisdesired calibration purpose. The control computer operative with thecontrol program is initially supplied with desired process parameters inregard to where each particular mill stand roll opening is presently setand so forth. The control program, for the here described calibration ofeach motor drive, is initialized through the provided programmersconsole by the operator. The control program then requests the lllldesired function program number and the motor drive system number whichis to be position optimized in regard to the calibration of the positionmovement slowdown profile curves. According to what is input at thisstage of the operation by the operator, for example, the first functionprogram might be the ACQUIR program which is address identified by a 1(for the ACQUIR function program) followed by a comma and then theparticular stand drive identification number (such as 01, 02, 03 and soforth). A branch operation would then be taken from the LOADER programto the desired function program. It is the purpose of the LOADER programto bring in each function program or subroutine program as may bedesired.

For each particular rolling mill stand, the present position error,which is the actual position compared to the desired reference position,is the position movement requested and will determine the speed ofoperation of the position regulated screwdown motor drive system inrelation to defined operation speeds of the screwdown motor drivesystem. An initial predetermined table of distance error points versusmotor drive system operating speed points, such as shown in TABLE TWO,is provided by the mill stand operator in accordance with the desiredoperation to be provided for each position regulated screwdown motordrive system for the respective stands of the rolling mill. Each motordrive system has a data file associated with it and one of the bases ofinformation in that data file is the speed versus distance curverelationship to define the desired position regulated operation of themotor drive system. If for example the desired accuracy band of thefinal positioning of the screwdown motor drive system is equal to 0.10inch, the defined operating speed corresponding to this accuracy band ofthe position regulated screwdown motor drive system may be 5 percent offull speed, with full speed being in the order of inches per second. Fora position error greater than 0.25 inch, the defined operating speed maybe 10 percent of full speed. For a position error greater than 0.75inch, the defined operating speed may be percent of full speed. For aposition error greater than 1.75 inches, the defined operating speed maybe percent of full speed. For a position error greater than 2.75 inches,the defined operating speed may be 30 percent of full speed. For aposition error greater than 20.00 inches, the defined operating speedmay be 60 percent of full speed. For a position error greater than 57.75inches, the defined operating speed may be 100 percent of full speed ina direction to correct the established position error. It should beunderstood, that the latter speed versus distance relationships are notthe same for every motor drive system, but rather are merelyillustrative of a typical speed distance profile defined for a screwdownposition motor drive system, and correspond to the down directionprofile curve set forth in TABLE TWO for a particular rolling millstand. The operator usually provides the defined operating speed points,such as 5, 10, 15, 20, 30, 60 and 100 percent respectively, and in theactual running operation of each screwdown motor drive system theposition error points of interest are initially established empirically,such as set forth in TABLE TWO. In other words, if it is desired by theoperator that if the actual position error is greater than 57.75 inchesthe screwdown motor drive system operates at percent of full speed untilthe 57.75 inches defined position error is reached, at which time thescrewdown motor drive system operates at 60 percent of full speed untilthe position error becomes 20.00 inches, at which time the speedreference to the screwdown motor drive system is changed to 30 percentof full speed until the position error becomes 2.75 inches, at whichtime the speed reference is changed to 20 percent of full speed untilthe position error becomes 1.75 inches, at which time the speedreference for the screwdown drive system becomes 15 percent of fullspeed until the position error becomes 0.75 inch, at which time thespeed reference for the screwdown drive system becomes 10 percent offull speed until the position error becomes 0.25 inch, at which time thespeed reference is changed to 5 percent of full speed until the positionerror becomes 0.01 inch, at which time the speed reference is changed tozero percent of full speed and the motor drive system stops. Theposition error distances at which the changes in speed reference shouldbe effected are initially determined empirically in the field.

In FIG. 3 there is shown a flow chart for the distance optimizationfunction program. The data file for a particular stand would have beenpreviously acquired through operation of the ACQUIR function program andmoved into the desired calibration area of core storage where it couldbe utilized and perhaps modified without disturbing the initial form ofthe data file which is still retained in the original and operating corestorage area. The speed versus distance profile curve is known, and itslocation in the data file is known from certain defined parameters inthe data file. At block 1 1 of FIG. 3 a check is made to be certain thatthe correct stand data file has been selected. The distance optimizationfunction program shown in FIG. 3 is called from the LOADER PROGRAM. Thesystem operator typed into the provided operators control unit theroutine desired function program number and the number identifying theparticular stand data file that is desired. This function program iscalled by an operator and not by the happening of some operation of therolling mill; initially, it could be done upon start-up of the rollingmill stand and in addition, if desired, it could be initiated upon eachchange of rolls for a given stand of the rolling mill. When a check ismade in FIG. 3 to see if the correct data file is present in thecalibration area of core storage, if it is not an error message isprinted at block 13 by the subroutine PRTMSG program to indicate thatthe wrong data file is in the calibration area. The error message ERR=40indicates that the error relates to the distance optimization functionprogram operation which is identified by 4, and the 0 indicates the typeof error. The program then goes to block 15 which returns to the controlof the LOADER program. On the other hand, if this is the correct standdata file, the program goes to block 17 where a subroutine programcalled PRODAT is entered into. The flow chart for this latter subroutineis shown in FIG. 12; this program is intended to set up desired profiledata information in regard to the maximum forward movement and themaximum reverse movement as well as the minimum forward and minimumreverse movements that are permitted and desired for the positionregulated motor drive system calibration operation.

1. The method of calibrating the slowdown operation of a motor drive,said method including the steps of: providing a first operation of saidmotor drive to establish a desired position movement in relation to adefined operating speed for said motor drive such that a minimum periodof time is required to effect said desired position movement;establishing the resulting position error of said motor drive inrelation to a desired position accuracy band; and providing a secondoperation of said motor drive to establish a calibrated positionmovement in relation to a change in said desired position movement forcorrecting said resulting position error.
 2. The method of claim 1operative with a programmed digital control computer having a storagememory, said method including the steps of: establishing a first datafile in said storage memory to define an initial slowdown operation ofsaid motor drive, and establishing a second data file in said storagememory to define a calibrated slowdown operation in accordance with saidcalibrated position movement of said motor drive.
 3. The method of claim1 operative with a plurality of desired operating speeds for said motordrive, said method including the step of: establishing a calibratedposition movement of said motor drive in relation to each of saiddesired operating speeds of said motor drive.
 4. The metHod of claim 1operative with a programmed digital control computer having a storagememory, said method including the steps of: providing an initial datafile in an operating area of said storage memory to determine saidslowdown operation of said motor drive, providing a calibrated data filein a calibration area of said storage memory to determine an optimumslowdown operation of said motor drive in accordance with saidcalibrated position movement, and replacing said first data file withsaid second data file in said operating area to control said motor drivein accordance with said optimum slowdown operation.
 5. The method ofclaim 1 for calibrating said slowdown operation in relation to aplurality of desired operating speeds for said motor drive, with saidsteps of providing first and second operations of said motor drive beingin relation to each of said desired operating speeds such that acalibrated position movement is established in relation to each of saiddesired operating speed.
 6. The method of claim 1 being operative inrelation to an initially defined slowdown profile for said motor drivein accordance with a defined operating speed for each of a plurality ofdesired position movements, with said step of providing a secondoperation being operative to establish a calibrated position movement inrelation to each defined operating speed.
 7. The method of calibratingthe position movement profile of a motor drive having a predeterminedspeed of operation in relation to each of at least two desired positionmovements, said method including the steps of: establishing a firstcalibrated position movement of said motor drive in relation to a firstpredetermined speed of operation; establishing a second calibratedposition movement of said motor drive in relation to a secondpredetermined speed of operation with said second speed of operationbeing greater than said first speed of operation; with at least one ofsaid first and second calibrated position movements being establishedsuch that an optimum period of time is required to effect saidcalibrated position movement; and with the step of establishing saidsecond calibrated position movement having as the initial reference forestablishing the second calibrated position movement the previouslyestablished first calibrated position movement.
 8. The method of claim 7operative with a programmed digital control computer having a storagememory, said method including the steps of: establishing a first datafile to define an initial position movement profile for determining theoperation of said motor drive, and establishing a second data file todefine a calibrated position movement profile in accordance with saidfirst and second calibrated position movements of said motor drive. 9.The method of claim 7 operative with a predetermined accuracy band forthe stopped position of said motor drive, said method including the stepof: establishing at least one of said first and second calibratedposition movements in relation to said accuracy band of said motordrive.
 10. The method of claim 7 operative with a programmed digitalcontrol computer having a storage memory, said method including thesteps of: providing an initial data file in an operating area of saidstorage memory to determine an initial position movement profile forcontrolling the operation of said motor drive, providing a calibrateddata file in a calibration area of said storage memory to determine anoptimum position movement profile in accordance with at least one ofsaid first and second calibrated position movements, and replacing saidfirst data file with said second data file in said operating area tocontrol the operation of said motor drive in accordance with saidoptimum position movement profile.
 11. The method of claim 7 forcalibrating said position movement profile in relation to a desiredstopping position accuracy band for said motor drive, wiTh said step ofestablishing a first calibrated position movement of said motor drivebeing a relation to said accuracy band; and with said step ofestablishing a second calibrated position movement of said motor drivebeing in relation to said accuracy band.
 12. The method of claim 7 beingoperative in relation to an initially defined position movement profilefor said motor drive in accordance with a defined operating speed foreach of a plurality of desired position movements, with said step ofestablishing a first calibrated position movement being operative toestablish a calibrated position movement S1 in relation to a firstpredetermined operating speed V1; and with said step of establishing asecond calibrated position movement being operative to establish acalibrated position movement S2 in relation to a second predeterminedoperating speed S2.
 13. A control system for calibrating the operationof a position regulated motor drive, in accordance with a slowdownprofile curve having a plurality of predetermined speed points, saidsystem including a programmed digital control computer having a storagememory, said control system comprising: means for moving a predeterminedinitial data file from a first operating area of said storage memory forcontrolling the operation of said motor drive into a second calibrationarea of said storage memory, means for calibrating said data file insaid second calibration area and in relation to establishing anoptimized position movement point for each of said speed points, withsaid means for moving being operative to move the calibrated data filefrom said second calibration area into said first operating area of saidstorage memory.
 14. The control system of claim 13, with said systemincluding means for establishing each of said optimized positionmovement points of said motor drive in relation to an initial desiredposition movement and such that a substantially optimum positioningoperation of said motor drive is thereby realized in relation to eachdesired position movement.
 15. In apparatus for calibrating a positionregulated motor drive system in relation to at least one initiallydesired position movement and a corresponding defined operating speedfor a position movement greater than said one initially desired positionmovement, with said apparatus including means for providing a firstoperation of said motor drive system in relation to said one desiredposition movement and said corresponding defined operating speed, meansfor determining the position error of said motor drive system inrelation to the resulting actual position of said motor drive system,and means for providing a second operation of said motor drive system inrelation to the same corresponding defined operating speed and saidposition error for determining a calibrated position movement of saidmotor drive system in relation to the latter defined operating speed.16. The control system of claim 15, with said apparatus being operativewith a programmed digital control computer having a storage memory, andwith said apparatus including, means for providing in a first operatingportion of said storage memory a first data file in accordance with aninitial slowdown profile curve including at least said one desiredposition movement for controlling the operation of said motor drivesystem, means for providing in a second calibration portion of saidstorage memory a calibrated second data file in accordance with at leastsaid calibrated position movement to define an optimized slowdownprofile curve for controlling the operation of said motor drive system,and means for moving said second data file from said second calibrationportion into said first operating portion of said storage memory.
 17. Acontrol system for calibrating the operation of a position regulatedmotor drive, in accordance with an initial data file providing aslowdown profile curve having a pluraliTy of desired position movementsset forth in relation to corresponding predetermined speed points, saidsystem including a programmed digital control computer having a storagememory, said system comprising: means for placing said initial data fileinto an operating area of said storage memory for controlling theoperation of said motor drive, means for moving said initial data filefrom said operating area of said storage memory into a calibration areaof said storage memory, means for calibrating said data file in relationto establishing an optimized position movement for each of saidplurality of desired position movements and corresponding to each ofsaid speed points, with said means for moving being operative to movethe calibrated data file back into said operating area of said storagememory for controlling the operation of said motor drive.
 18. A controlsystem for a position regulated motor drive system having apredetermined positioning accuracy band and a plurality of definedoperating speeds, with said system including means for providing a firstoperation of said motor drive to establish a first position movement inrelation to one of said defined operating speeds, means for comparingthe resulting position of said motor drive system with said accuracyband to determine what position error is present, means for establishinga calibrated position movement for said motor drive system in accordancewith said position error, and means for providing a second operation ofsaid motor drive in relation to said calibrated position movement and inrelation to said one defined operating speed.
 19. The control system ofclaim 18, with said system being operative with a programmed digitalcontrol computer having a storage memory, and with said systemincluding, means for providing a first data file in an operating portionof said storage memory in accordance with an initial slowdown profilecurve for controlling the operation of said motor drive system, meansfor providing a second data file in a calibration portion of saidstorage memory in accordance with at least said calibrated positionmovement to define an optimized slowdown profile curve for controllingthe operation of said motor drive system, and means for moving saidsecond data file from said calibration portion into said operatingportion of said storage memory.
 20. The control system of claim 18, withsaid means for providing a first operation and said means for providinga second operation being operative in regard to each of said pluralityof defined operating speeds.
 21. The method of calibrating the operationof a position regulated actuating mechanism, said method including thesteps of: establishing a first calibrated operation of said actuatingmechanism in relation to a desired first operating speed and apredetermined position accuracy band; establishing a second calibratedoperation of said actuating mechanism in relation to a desired secondoperating speed and said position accuracy band; with the step ofestablishing said second calibrated operation having as the initialreference for establishing the second calibrated operation the firstcalibrated operation of said actuating mechanism.
 22. The method ofclaim 21, for calibrating the position movement of said actuatingmechanism, said method including said first calibrated operation being afirst position movement S1 in relation to a first operating speed V1 andsaid second calibrated operation being a second position movement S2 inrelation to a second operating speed V2.
 23. The method of claim 21,wherein at least the step of establishing a second calibrated operationof said actuating mechanism includes the operation of a programmeddigital computer to sense the operation of said actuating mechanism inrelation to said first calibrated operation of said actuating mechanism.24. The method of calibrating the slowdown profile curve of a positionRegulated actuating mechanism, said method including the steps of:providing at least a first operation of said actuating mechanism toestablish a first position movement in relation to a predeterminedposition accuracy band and in relation to a first desired speed ofoperation, such that said actuating mechanism is stopped within saidaccuracy band in a minimum period of time; providing at least a secondoperation of said actuating mechanism to establish a second positionmovement in relation to said first position movement and in relation toa second desired speed of operation such that said actuating mechanismis stopped within said accuracy band in a minimum period of time; withat least the step of establishing said second calibrated operationhaving as a position reference for establishing the second positionmovement the previously established first position movement of saidactuating mechanism.
 25. The method of claim 24, wherein at least thestep of providing a second operation of said actuating mechanismincludes the operation of a programmed digital computer to establish aposition movement of said actuating mechanism.